Players of "rock-paper-scissors" unconsciously mimic the actions of their opponents.

If both players made their choices of rock, paper, or scissors truly randomly without any outside input, there would only be a 1 in 3 chance of the game ending in a draw. Studies have shown that two blindfolded players who can’t see what their opponents are doing do exactly this; they tie 33.3% of the time. However, when one player is blindfolded, and his opponent isn’t, the chances of a draw occurring increase to 36.3%. The same study found that when the blindfolded player chooses either rock, paper or scissors before his opponent, the opponent is even more likely to make the same decision. This points toward a natural inclination in humans to imitate their peers, even when it costs them a chance to win a game. Scientists refer to this as “automatic imitation”.
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